Profit optimization in biogas plants via flexible feed rate and flexible energy production

• Simulation of a biogas plant with flexible feed rate and flexible energy production. • Adaptive control and model predictive control based on linear programming. • Analysis with various electricity prices, government subsidies, and substrate costs. • Increased profits through flexibility without additional investment. • Flexibility in biogas production without overbuilding. Achieving fully flexible operations of biogas plants poses major challenges. The complexity of modeling the anaerobic digestion process and the various kinds of feedstock used in each plant make it difficult to develop a universal solution. Nevertheless, increasing the flexibility of biogas plant operation can boost profitability. This is becoming increasingly important, particularly considering declining government subsidies for biogas plants. A major criticism of many existing solutions is the need for additional combined heat and power plants in order to fully exploit the advantages of this flexibility, which leads to higher investment costs. This study develops a Flexible Feed Rate with Flexible Energy Production Scenario, based on the combination of model predictive control and adaptive control. This method is compared with other state of the art methods and evaluated over ten years, considering electricity prices, various government subsidies, changing substrate costs, and investment costs for the number of combined heat and power plants installed. The results show that the Flexible Feed Rate with Flexible Energy Production Scenario can achieve higher profits with minimal investment costs. The need for large gas storage facilities can also be reduced with the implementation of this fully flexible biogas operation method.